I have a 1990 Jeep Cherokee that was running great except it would overheat when hauling a boat. Today I put in a cooling system from a 1992 Cherokee to switch from the closed radiator to an open one. After everything was complete when I cranked it, it would instantly crank up then go dead, even if I gave it gas after it cranked it just goes dead. Any ideas where to start looking.

 

did you unplug anything in the process that would have an effect on this?

 

Not that I am aware of.

 

did you put the plug back into the thermostat housing?

 

go through and double check anything and everything that was in the area you were working in. Something could have been bumped or unplugged and forgot. done that before.

 

Yes as has been mentioned double check everything. Nothing in the cooling system normally would cause your problem. But also as has been mentioned check the sensor on the housing as that could also affect other areas unrelated

 

Check to see if you knocked the wire off the ballast resistor on the driver's side inner fender near the air cleaner.

 

does it start every time you turn the key and then it dies on you or does it crank and crank then starts some of the time?

 

THIS. If the ballast resistor is bad or out of circuit, the engine will start and run briefly, then stall.